A related art power tool includes a motor such as a brushless DC motor. In the power tool, a switching device, such as an FET, for driving the brushless DC motor is frequently turned on and off to precisely control the rotation of the motor so that, for example, the rotation speed is maintained constant in a case where a battery output starts to fall down.
However, frequently turning the switching device on and off causes a generation of intense heat due to switching loss.
Accordingly, a motor control board equipped with the switching device is cooled by, for example, a cooling fan. The cooling fan sucks air from an inlet port provided in a housing thereby to generate cooling air to cool the motor or the control board using the air. The air for use in the cooling is discharged from an outlet port provided in the housing. In general, the cooling fan is disposed coaxially with the motor.
If the motor control board is disposed on an axis of the motor, the motor control board is effectively cooled. However, an axial size of the tool is increased.
JP 4436033 B2 discloses a configuration capable of reducing an entire size of the tool, in which a motor control board is disposed in a space between a motor and a trigger switch, a plurality of switching devices are mounted on the motor control board in a state in which the elements are fixed to an L-shaped heat sink, and the heat sink is disposed at a rear of the motor in an axial direction.